The present invention relates to a DNA fragment that is cap encoding rubber polymerase, also known as rubber transferase, and to a hybrid vector and a transformed host, each comprising the DNA fragment The present invention also relates to a process of producing rubber in vitro and a process of producing rubber in vivo.
According to 13 ENCYCLOPEDIA OF POLYMER SCIENCE AND ENGINEERING 687, 2nd ed., John Wiley & Sons, Inc., (1988), natural rubber, cis-1,4-polyisoprene, is produced naturally in over 200 species of plants Two of these plants, Hevea brasiliensis and Parthenium argentatum ("guayule") produce sufficiently high molecular weight rubber to be utilized for commercial production of natural rubber.
Efforts have been made to increase the production of rubber in rubber-producing plants by selection and breeding of improved planting material or better methods of tapping and general husbandry, or by chemically stimulating the yield. Despite such efforts, however, the amount of rubber such plants can produce or can be stimulated to produce, is limited by the rate of rubber synthesis by the plant.
The biochemical pathway leading to the production of rubber has been studied and is believed to involve at least 17 steps starting from simple sugars, each step being mediated by an enzyme. Rubber Developments, 34: 96-98 1981. One enzyme, rubber polymerase, has been substantially purified and is believed to mediate the polymerization of isopentenyl pyrophosphate ("IPP") onto an allylic pyrophosphate to produce rubber, as described in U.S. Pat. No. 4,638,028, the contents of which are incorporated herein by reference.